Priority Claim: Pursuant to the provisions of 35 USC .sctn. 119(e), this application claims the priority of Provisional Patent Application Ser. No. 60/015,776, filed Apr. 16, 1996 for "BOWSTRING."
1. Field of the Invention
This invention pertains to bowstrings for archery bows. It is particularly directed to bowstrings having multiple strands of braided construction.
2. State of the Art
Modern archery bowstrings comprise a plurality of individual strands gathered together in a central nocking region and at respective common ends. Typically, the individual strands comprise bundles of twisted fibers. These bowstrings are conventionally provided with "servings" in the areas where abrasion resistance is crucial, such as where an arrow is nocked, or on the end loops which connect to the limbs of a bow. A serving typically comprises a line of relatively small diameter wound around the bowstring transverse its individual strands. Servings prevent abrasion damage to the string, and provide an attachment surface for nock sets or other indicators intended to guide proper placement of an arrow nock with respect to the string.
Typical problems encountered by archers using conventional bowstrings include stretch or creep. U.S. Pat. No. 4,957,094 describes some of the adjustment problems associated with string stretch in compound bows. Migration of servings is another frequent complaint. Servings sometimes cut into the individual strands of a conventional bowstring, thereby creating regions of stress concentration, a condition which often leads to premature breakage.
Braiding is a well established method of fabric formation. A braid structure is formed by the diagonal intersection of yarns, generally without the warp and/or filling yarns conventionally present in woven fabrics. A twisted fiber bundle may function as a yarn in braiding technology. Two-dimensional circular or flat braids are formed by crossing individual yarns alternately over and under one or more intersecting yarns in a repeating pattern. Common braid designs include "diamond," "regular," and "hercules," which are structured with 1/1, 2/2 and 3/3 intersection repeats, respectively, all as explained by the publication Wellington Sears Handbook of Industrial Textiles, Sabit Adanur, Technomic Publishing Co., Inc., Lancaster, Pa. (1995).
Triaxial braiding introduces axial yarns to the braid structure. These yarns do not generally interlace with the diagonal yarns, being trapped in place between those interlacing sets. Triaxial braids are especially useful for composite yarns. "Circular" (also called "tubular" or "round") braids may be either hollow or "solid" the later being formed around an axial center core. Circular braids are formed from an even number of yarns. A solid braid of this type is composed of a "sleeve" and a core. The core may be of any selected shape and material composition. By contrast, flat braids are formed as a flat strip or tape. "Plain" flat braids are constructed from an uneven number of yarns, while diamond flat braids are formed from an even number of yarns. Other braided structures may be formed through three-dimensional braiding techniques.